JavaScript Program to Check if a Key Exists in an Object

Example 1: Check if Key Exists in Object Using in Operator

// program to check if a key exists

const person = {
    id: 1,
    name: 'John',
    age: 23
}

// check if key exists
const hasKey = 'name' in person;

if(hasKey) {
    console.log('The key exists.');
}
else {
    console.log('The key does not exist.');
}

Output

The key exists.

In the above program, the in operator is used to check if a key exists in an object. The in operator returns true if the specified key is in the object, otherwise it returns false.

Example 2: Check if Key Exists in Object Using hasOwnProperty()

// program to check if a key exists

const person = {
    id: 1,
    name: 'John',
    age: 23
}

//check if key exists
const hasKey = person.hasOwnProperty('name');

if(hasKey) {
    console.log('The key exists.');
}
else {
    console.log('The key does not exist.');
}

Output

The key exists.

In the above program, the hasOwnProperty() method is used to check if a key exists in an object. The hasOwnProperty() method returns true if the specified key is in the object, otherwise it returns false.